Dry silicone gels and their methods of making

ABSTRACT

Methods and systems are provided for a dry silicone gel. The dry silicone gel comprises a base polymer having a vinyl-silicone group, a crosslinker, and a chain extender. The dry silicone gel may be made by reacting (a) a first set of components comprising a base polymer having a vinyl-silicone group and an addition cure catalyst with (b) a second set of components comprising a crosslinker, a chain extender, and additional base polymer. In certain circumstances, the base polymer and additional base polymer are vinyl-terminated polydimethylsiloxane.

REFERENCE TO RELATED APPLICATION

Reference is made to U.S. Patent Application entitled “Closure andInterconnect Systems and Methods of Using Dry Silicone Gels in Closureand Interconnect Systems,” filed the same day as the presentapplication. This entire co-pending application is incorporated byreference.

BACKGROUND

Closure systems are used to protect internal components from degradationcaused by external environments. For example, internal components suchas fiber optic cables and copper cables are often enclosed in closuresystems. Examples of commercially available closure systems include theOutdoor Fiber Drop Repair (OFDR), the Outdoor Fiber Distribution Closure(OFDC), and the Fiber optic Infrastructure System Technology (FIST),available from Tyco Electronics, Kessel-Lo, Belgium. In particular, theOFDR Closure is used to break out fibers from a looped fiber optic cableto connect users such as business customers or persons in multiple orsingle living units. These types of closures can be used in aerial,pedestal, and underground environments. Other closure systems arecommercially available for use with communication and energytransmission cables.

Closure systems typically include internal components such as fiberorganizers, cable seals and termination devices, drop cable seals for anumber of drops with drop cable termination devices, and universalsplice holders for a number of splices. These internal components may besubject to environmental factors such as varying moisture levels, heatand cold, and exposure to other chemical substances. The closure systemsare preferably protected from damage with a sealant of some sort.Conventional sealants, however, suffer from a number of drawbacks thatmake them unsuitable for certain closure systems.

Sealants are often used for insulation and for protection against water,corrosion and environmental degradation, and for thermal management.Prior to now, a number of sealants have been known; however, currentlyavailable sealants have certain drawbacks and disadvantages that makethem inadequate for specific uses and for use in contact with certainmaterials. In particular, there is an unmet need for sealants that aresuitable for fiber optic and electronic closure systems.

Suitable sealing systems for closures are needed for use with a varietyof different cables. For examples, a sealing system is needed for cablestermed Low Smoke Zero Halogen (“LSZH”), also known as Low Smoke HalogenFree (“LSHF”), Low Smoke Zero Halogen (“LSOH”), and Zero Halogen LowSmoke (“OHLS”) among other things.

LSZH cables are characterized by containing no halogenatedflame-retardants, and produce relatively limited amounts of smoke whenexposed to sources of heat such as a flame or heated wires. LSZH cablesprovide an alternative to the frequently used polyethylene, PVC, orthermoplastic urethane coatings. Polyethylene, PVC, or thermoplasticurethane, when they contain halogens, may produce hazardoushalogen-containing compounds such as HCl or HBr gas. An improvement tocurrent LSZH cable closure systems is needed to enhance performance inenvironmentally sensitive environments.

Traditionally, thermoplastic oil gels have been used in LSZH closuresystems. A problem, however, with thermoplastic gels used as sealants,and in closure systems in general, is that they often contain highamounts of mineral oil. A problem has been observed with oil-containinggels in that they may leak oil. The oil in these gels may leak from thegel and cause deterioration, discoloring, or degradation of the cable inthe closure system. In some extreme cases, a cable may even snap undercompression due to the damage done by the oil leaking from thethermoplastic gel. There exists an unmet need for alternatives to oilcontaining gels. Presently available alternatives to oil-containinggels, however, have not provided such a solution. For one, sealantsother than oil-containing gels may have one or more undesirableproperties. Examples of undesirable properties include excessivehardness, inadequate temperature resistance (e.g., flammability or atendency to become brittle with cold, i.e., inadequate glass transitiontemperature) and viscoelastic properties, chemical incompatibility, highwater absorption, and hydrolytic instability. Accordingly there existsan unmet need for closure systems with suitable hardness, viscoelasticproperties, low permanent set or compression set, long-term performance(e.g., >20 years), amongst other properties.

In contrast to oil-containing thermoplastic gels, dry silicone thermosetgels contain relatively low, or do not contain at all, amounts ofdiluent fluids such as unreactive silicone oil or mineral oil. A drysilicone gel, instead of being a thermoplastic gel, is a thermoset gel.Thermoset gels can be produced by chemical crosslinking. Examples ofthermoset gels are silicone dry gels and polyurethane gels. A drysilicone gel makes no use of an extra solvent or diluent fluid but canstill be categorized under the term “gel” because of the similarity inphysical properties and behavior, or because of its viscoelasticproperties. Dry silicone gels are however used more rarely than freeoil-containing gels for a number of reasons. For example, dry siliconegels are rare because they are more expensive and difficult to processthan certain other types of gels. Accordingly, there exists an unmetneed for an improved dry silicone gel and an improved method ofpreparing a dry silicone gel.

U.S. Pat. No. 7,489,844 discloses fiber optic cable with a suspensionliquid surrounding the optical fiber. The suspension oil may be mineraloil or a blend of oil and silica.

U.S. Pat. No. 6,091,871 discloses a reinforced optical fiber cable thatincludes a protective tube for protecting optical fibers, a reinforcinglayer, and reinforcing rods around the protective tube, together with anouter sheath. The inside space in which the optical waveguides arereceived contains a filler material to protect the optical waveguidesagainst penetration of moisture.

U.S. Pat. No. 6,167,178 discloses a fiber optic cable including at leastone optical fiber having a buffer layer formed of a flame-retardantpolyolefin material. The flame-retardant polyolefin material is tightlyformed about the optical fiber, thereby defining a tight buffer layer, alayer of strength members, and a cable jacket surrounding optical fibersin contact with at least some strength members.

U.S. Pat. No. 7,522,795 discloses a loose tube optical waveguide cablewith two or more optical waveguides with a single protective tube, orsheath for environmental protection. The cable contains no gel-likecompounds and no strengthening elements.

BRIEF SUMMARY

In one embodiment, a method is provided of making a dry silicone gel.The method comprises providing a first set of components comprising: (1)a base polymer having a vinyl-silicone group, and (2) an addition curecatalyst. The method further comprises providing a second set ofcomponents comprising: (1) a crosslinker, (2) a chain extender, and (3)additional base polymer. The method further comprises mixing the firstand second set of components together to form the dry silicone gel. Insome embodiments of the method, the second set of components may furthercomprise an inhibitor. In one embodiment, the inhibitor is3,5-dimethyl-1-hexyn-3-ol. In certain embodiments of the method, thefirst and/or second set of components may further comprise at least oneadditive selected from the group consisting of: flame retardants,coloring agents, adhesion promoters, stabilizers, fillers, dispersants,flow improvers, plasticizers, slip agents, toughening agents, andcombinations thereof. In some embodiment, the dry silicone gel comprisesbetween 0.1 wt % and 25 wt % of a flame retardant additive. In oneembodiment, the flame retardant additive is zinc oxide.

In some embodiments of the method, the base polymer and additional basepolymer are each a vinyl-terminated polydimethylsiloxane. In certainembodiments of the method, the base polymer and additional base polymereach have one or more of the following properties: (1) a molecularweight between 28,000 g/mol and 70,000 g/mol, (2) a viscosity between500 mm²/s and 165,000 mm²/s, and/or (3) a vinyl content between 0.01mmol/g and 0.1 mmol/g.

In other embodiments of the method, the dry silicone gel comprises oneor more of the following properties: (1) a hardness between 100 grams(“g”) and 300 g as measured on a TA-XT2 texture analyzer from TextureTechnologies, (or between 26-53 Shore 000 Hardness), (2) a stressrelaxation between 40% and 60% when the gel is subjected to adeformation of 50% of its original size, (3) a compression set between4% and 20% after 50% strain has applied to the gel for 1000 hours at 70°C., and (4) less than 10% oil bleed out after being under compression of1.2 atm for 60 days at 60° C.

In certain embodiments of the method, the crosslinker is selected fromthe group consisting of tetrakis(dimethylsiloxy)silane,methyltris(dimethylsiloxy)silane, and combinations thereof. In otherembodiments, the chain extender is selected from the group consisting ofhydride containing polydimethylsiloxane, dihydride containing siloxane,hydride terminated polydimethylsiloxane, hydride terminatedpolyphenylmethylsiloxane, hydride terminated polydiphenylsiloxane,functionalized terminated silicone, and combinations thereof.

In some embodiments of the method, the dry silicone gel has a molefraction of hydride present as crosslinker between 0.2 and 0.5. In otherembodiments, the hydride to vinyl ratio in the dry silicone gel isbetween 0.8 and 1.0. In yet other embodiments, the catalyst is selectedfrom the group consisting of platinum complexed withdivinyltetramethyldisiloxane and rhodium chloride complex. In stillother embodiments, the weight percent ratio between the first set ofcomponents and the second set of components is 1:1.

In another embodiment, a method is provided of making a dry siliconegel. The method comprises providing a first set of componentscomprising: (1) a vinyl-terminated polydimethylsiloxane having amolecular weight between 28,000 g/mol and 70,000 g/mol, a viscositybetween 3,000 mm²/s and 7,000 mm²/s, and a vinyl content between 0.01mmol/g and 0.1 mmol/g, and (2) an addition cure catalyst, wherein thecatalyst is selected from the group consisting of platinum complexedwith divinyltetramethyldisiloxane and rhodium chloride complex. Themethod further comprises providing a second set of componentscomprising: (1) a crosslinker selected from the group consisting oftetrakis(dimethylsiloxy)silane, methyltris(dimethylsiloxy)silane, andcombinations thereof, (2) a chain extender selected from the groupconsisting of hydride containing polydimethylsiloxane, dihydridecontaining siloxane, hydride terminated polydimethylsiloxane, hydrideterminated polyphenylmethylsiloxane, hydride terminatedpolydiphenylsiloxane, functionalized terminated silicone, andcombinations thereof, (3) an inhibitor, and (4) additionalvinyl-terminated polydimethylsiloxane having a vinyl-terminatedpolydimethylsiloxane having a molecular weight between 28,000 g/mol and70,000 g/mol, a viscosity between 3,000 mm²/s and 7,000 mm²/s, and avinyl content between 0.01 mmol/g and 0.1 mmol/g. The method furthercomprises mixing the first and second set of components together to formthe dry silicone gel, wherein the dry silicone gel has a mole fractionof hydride present as crosslinker between 0.2 and 0.5, wherein thehydride to vinyl ratio in the dry silicone gel is between 0.8 and 1.0,and wherein the weight percent ratio between the first set of componentsand the second set of components is 1:1.

In another embodiment, a dry silicone gel composition is provided. Thedry silicone gel comprises a base polymer having a vinyl-silicone group.The gel further comprises a crosslinker. The gel further comprises achain extender. In certain embodiments of the composition, the gelfurther comprises at least one additive selected from the groupconsisting of: flame retardants, coloring agents, adhesion promoters,stabilizers, fillers, dispersants, flow improvers, plasticizers, slipagents, toughening agents, and combinations thereof.

In some embodiments of the composition, the base polymer is avinyl-terminated polydimethylsiloxane. In other embodiments, thecrosslinker is selected from the group consisting oftetrakis(dimethylsiloxy)silane, methyltris(dimethylsiloxy)silane, andcombinations thereof. In yet other embodiments, the chain extender isselected from the group consisting of hydride containingpolydimethylsiloxane, dihydride containing siloxane, hydride terminatedpolydimethylsiloxane, hydride terminated polyphenylmethylsiloxane,hydride terminated polydiphenylsiloxane, functionalized terminatedsilicone, and combinations thereof.

In certain embodiments of the composition, the gel has a mole fractionof hydride present as crosslinker between 0.2 and 0.5. In otherembodiments, the gel has a hydride to vinyl ratio between 0.8 and 1.0.In yet other embodiments, the dry silicone gel comprises between 0.1 wt% and 25 wt % of a flame retardant additive. In some embodiments, theflame retardant additive in the dry silicone gel is zinc oxide.

In yet other embodiments, the base polymer has one or more of thefollowing properties: (1) a molecular weight between 28,000 g/mol and70,000 g/mol, (2) a viscosity between 500 mm²/s and 165,000 mm²/s, and(3) a vinyl content between 0.01 mmol/g and 0.1 mmol/g.

In other embodiments, the gel comprises one or more of the followingproperties: (1) a hardness between 100 g and 300 g (26-53 Shore 000Hardness), (2) a stress relaxation between 40% and 60% when the gel issubjected to a deformation of 50% of its original size, (3) acompression set between 4% and 20% after 50% strain has applied to thegel for 1000 hours at 70° C., and (4) less than 10% oil bleed out afterbeing under compression of 1.2 atm for 60 days at 60° C.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a graph showing the hardness (g) verses stress relaxation (%)of dry silicone gels as measured on a TA-XT2 texture analyzer fromTexture Technologies (Westchester County, N.Y.). The squares provideexamples of gels that are tight and re-enterable; the red trianglesprovide examples of gels that fail on “tightness” and/or “re-entry.” Thesolid oval in the bottom left of the graph indicates examples oftraditional thermoplastic elastomer gels. The solid oval to the rightindicates a specific region for dry silicone gels. Three examples of drysilicone gel are shown within the oval. The dotted oval indicates anextended range of acceptable dry silicone gels.

FIG. 2 is a graph showing the stress relaxation (%) versus thecompression set (%) of dry silicone gels over 1000 hours at 70° C. Thecompression set was measured using a modified version of ASTM D395,method B. As opposed to using samples with a diameter of 29 mm athickness of 12.5 mm, samples were measured having a diameter of 28 mmand thickness of 12 mm. The squares provide examples of gels that aretight and re-enterable; the red triangles provide examples of gels thatfail on tightness and/or re-entry. The solid oval on the left of thegraph indicates examples of traditional thermoplastic elastomer gels.The solid oval to the lower right indicates a specific region for drysilicone gels. Three examples of dry silicone gel are shown within theoval. The dotted oval indicates an extended range of acceptable drysilicone gels.

FIG. 3 is a graph showing the hardness (g) versus the compression set(%) of dry silicone gels over 1000 hours at 70° C. Again, compressionset was measured with the modified version of ASTM D395, method Bdescribed above. The squares provide examples of gels that are tight andre-enterable; the red triangles provide examples of gels that fail ontightness and/or re-entry. The solid oval on the left of the graphindicates examples of traditional thermoplastic elastomer gels. Thesolid oval to the lower right indicates a specific region for drysilicone gels. Three examples of dry silicone gel are shown within theoval. The dotted oval indicates an extended range of acceptable drysilicone gels.

FIG. 4 is a graph showing the oil bleed-out of five gels undercompression at a pressure of about 120 kPa (about 1.2 atm) and at atemperature of about 60° C. The gels labeled Si H140, Si H 170, and SiH200 are dry silicone gels having hardnesses of 140 g, 170 g, and 200 g,respectively. The gels labeled L2912 and L2908 are examples ofthermoplastic elastomer gels.

FIG. 5 is a graph showing a theoretical stoichiometric curve comparingthe hardness of the dry silicone gel as a function of the mole fractionof hydride content in the crosslinker (“MFHC”) and the hydride/vinylratio (“H/V”).

FIG. 6 is a depiction of an interconnect system having a connection hubhaving multiple connection ports or receptacles for the connector,housing, and cable components to be connected.

FIG. 7 is a depiction of a connector, housing, and cable assembly withradial sealing.

FIG. 8 is a depiction of a connector, housing, and cable assembly withaxial sealing.

FIGS. 9a and 9b are depictions of a straight two piece housing assemblydesigned for axial sealing.

FIGS. 10a and 10b are depictions of an angled two piece housing assemblydesigned for axial sealing.

DETAILED DESCRIPTION

As used herein, terms such as “typically” are not intended to limit thescope of the claimed invention or to imply that certain features arecritical, essential, or even important to the structure or function ofthe claimed invention. Rather, these terms are merely intended tohighlight alternative or additional features that may or may not beutilized in a particular embodiment of the present invention.

As used herein, the terms “comprise(s),” “include(s),” “having,” “has,”“contain(s),” and variants thereof, are intended to be open-endedtransitional phrases, terms, or words that do not preclude thepossibility of additional acts or structure.

Any concentration range, percentage range, or ratio range recited hereinare to be understood to include concentrations, percentages, or ratiosof any integer within that range and fractions thereof, such as onetenth and one hundredth of an integer, unless otherwise indicated. Also,any number range recited herein relating to any physical feature are tobe understood to include any integer within the recited range, unlessotherwise indicated. It should be understood that the terms “a” and “an”as used above and elsewhere herein refer to “one or more” of theenumerated components. For example, “a” polymer refers to one polymer ora mixture comprising two or more polymers.

As used herein, the term “dry silicone gel” may refer to a chemicallycrosslinked polymer having a Si—O backbone and comprising a relativelylow amount, or no amount at all, of diluent fluids such as silicone oilor mineral oil. As opposed to carbon-based polymers, the crosslinkedsilicone polymers of dry silicone gels are based on a Si—O backbone. Thecharacteristics of silicon and oxygen provide crosslinked polymers withtheir exceptional properties. For example, silicon forms stabletetrahedral structures, and silicon-oxygen bonds are relatively strongwhich results in dry silicone gels with high temperature resistance. Inaddition, crosslinked Si—O polymers have a relatively high chainflexibility as well as low rotational energy barrier.

The dry silicone gels may be made according to a number of differentpolymerization reactions. In certain embodiments, the polymerizationreaction is a hydrosilylation reaction, also referred to as ahydrosilation reaction. In some embodiments, the hydrosilylationreaction makes use of a platinum catalyst, while other embodiments makeuse of radicals. In further embodiments, the dry silicone gel is made bya dehydrogenated coupling reaction. In other embodiments, the drysilicone gel is made by a condensation cure RTV reaction.

In certain embodiments, the dry silicone gel is made by reacting atleast a crosslinker, a chain extender, and a base polymer (e.g., avinyl-terminated polydimethylsiloxane). In certain embodiments, acatalyst is included to speed up the reaction. In additionalembodiments, an inhibitor may be used to slow down the rate of reaction.The components of the dry silicone gels, their resulting properties, andtheir end-use are described in greater detail below.

In certain embodiments, the dry silicone gel is made by an addition cureor platinum cure reaction mechanism. In some embodiments, the mechanismemploys the use of a catalyst. By using a catalyst, the activationenergy of the reaction is lowered and faster curing times at lowertemperatures can be achieved. A schematic overview of the platinum curereaction mechanism is shown below in (I).

For the reaction in (I) to be made possible, two functional groups mustreact with each other. In certain embodiments, the two functionalitiesare (1) the Si—H group and (2) the Si-vinyl group. These twofunctionalities may be provided by: (1) a base polymer, (2) acrosslinker, and (3) a chain extender.

Base Polymer

In certain embodiments, the Si-vinyl group is provided by a base polymersuch as a vinyl terminated polydimethylsiloxane (otherwise referred toas “V-PDMS”), which is shown below in (II). In this example, the basepolymer compound comprises a vinyl group at each end of the compound.

In certain embodiments, the molecular weight, of the base polymer iscontrolled through anionic ring-opening polymerization of cyclicsiloxanes in the presence of alkali-metal hydroxide of a base that isvolatile (e.g., tetramethylammonium silanolate). Endcapping of the PDMSwith a vinyl group is needed, so these groups are added to thepolymeriztion mixture. V-PDMS together with the chain extender determinethe molecular weight between the different crosslink sites.

The vinyl-containing base polymer, such as V-PDMS, may have differentviscosities that affect the resulting dry silicone gel. In general, ahigh molecular weight V-PDMS will produce an uncured gel with a higherviscosity. In certain embodiments, a low molecular weight V-PDMSgenerally improves processability. In other embodiments, the V-PDMS usedin the dry silicone gel has a viscosity between approximately 500 and165,000 cSt (500-165,000 mm²/s), between approximately 1000 cSt and50,000 cSt (1000-50,000 mm²/s), between approximately 3000 cSt and 7000cSt (3000-7000 mm²/s), or between approximately 4500 cSt and 5500 cSt(4500-5500 mm²/s).

In some embodiments, the vinyl-terminated polydimethylsiloxane has amolecular weight between about 20,000 g/mol and about 50,000 g/mol. Inother embodiments, the vinyl-terminated polydimethylsiloxane has amolecular weight between about 50,000 g/mol and about 80,000 g/mol. Inyet other embodiments, the vinyl-terminated polydimethylsiloxane has amolecular weight between about 28,000 g/mol and about 72,000 g/mol. Inone particular embodiment, the vinyl-terminated polydimethylsiloxane hasa molecular weight of approximately 49,500 g/mol.

In certain embodiments, the base polymer contains between approximately1 and 10 mol of vinyl per 500,000 g/mol of V-PDMS. In one embodiment,the base polymer contains approximately 2 mol of vinyl per 200,000 g/molof V-PDMS (the vinyl end group concentration would be in the order of10⁻⁵). In yet other embodiments, the vinyl content of the V-PDMS isbetween approximately 0.01 and 0.1 mmol/g, or between approximately0.036 and 0.07 mmol/g.

Crosslinker

In certain embodiments, the Si—H end groups for the reaction in (I) maybe provided by a crosslinker and/or a chain extender. A crosslinker iscapable of forming connections between vinyl-terminatedpolydimethylsiloxane chains. In certain embodiments, the crosslinkerincludes electronegative substituents such as alkylsiloxy or chlorine.In one embodiment, the crosslinker comprises four Si—H groups that arecapable of forming a connection point between four differentvinyl-terminated polydimethylsiloxane chains. In some embodiments, thecrosslinker is tetrakis (dimethylsiloxy)silane, shown below in (III). Inother embodiments, the crosslinker is methyltris(dimethylsiloxy)silane.Other crosslinkers may also be used. Using higher functionalcrosslinkers is also possible, but these form less defined polymerstructures.

Chain Extender

In addition to the crosslinker, the Si—H end group may be provided by achain extender, wherein both ends of the chain extender compound areterminated with a Si—H group. In certain embodiments, the chain extendercomprises reactive groups that are compatible and are willing to reactwith the vinyl groups in the base polymer. Just as for the crosslinker,these groups are Si—H groups that can react in a hydrosilation reaction.The chain extender typically includes two functional groups; however,the chain extender may include three or more functional groups, suchthat the chain extender functions as a branching agent. The functionalgroups may be the same as or different than each other. The functionalgroups may also be the same as or different than the functional groupsof the first component and/or the second component.

The chain extender may be any chain extender known in the art. In oneembodiment, the chain extender is a hydride containingpolydimethylsiloxane. In another embodiment, the chain extender is ahydride terminated polydimethylsiloxane, shown below in (IV).

In a further embodiment, the chain extender is a hydride terminatedpolyphenylmethylsiloxane. In another embodiment, the chain extender is ahydride terminated polydiphenylsiloxane. In yet another embodiment, thechain extender is a dihydride containing siloxane. The chain extendermay have a high molecular weight or a low molecular weight. The chainextender may also be branched or unbranched. In other embodiments, thechain extender is a high molecular weight polydimethylsiloxane. In otherembodiments, the chain extender is a low molecular weightpolydimethylsiloxane.

In other embodiments, the chain extender is a functionally-terminatedsilicone such as a silanol terminated, vinyl terminated, and aminoterminated polydimethylsiloxane. Such silicones have low tear strengthand can be toughened by incorporating fumed silica (SiO₂) into thestructure. For example, an alkoxy-functionalized siloxane can beincluded. Suitable alkoxy-functionalized siloxanes includepolydiethoxysiloxane, tetraethoxy silane, tetramethoxy silane, andpolydimethoxy siloxane. In other embodiments, the chain extender is afluorosilicone, phenyl silicone, or a branching diethyl silicone.

In certain embodiments, by making use of the chain extender molecule,the V-PDMS base polymer can be shorter because the H-PDMS chain extenderwill extend the V-PDMS base polymer chain in situ between twocrosslinker compounds. By using this mechanism, a V-PDMS chain of ashorter length can be applied which leads to lower viscosities andcompounds that are easier to work with. Therefore, lower viscosity basepolymer compounds can be used unlike a peroxide activated cure reactionmechanism. For example, a peroxide activated cure mechanism makes use ofpolymer chains with viscosities of approximately 2,000,000 cSt(2,000,000 mm²/s) while in the platinum cure mechanism allows for basepolymer chains (V-PDMS) having viscosities of approximately 5,000 cSt(5,000 mm²/s).

MFHC and H/V Ratios

The amounts of crosslinker and chain extender that provide the hydridecomponent may be varied. In certain embodiments, the amount of hydridein the gel is defined in terms of the mole fraction of hydride presentas crosslinker (“MFHC”). For example, when the MFHC value is 0.3 or 30%,this means that 30% of the hydrides present in the system are part ofthe crosslinker and the remaining 70% of the hydrides are provided bythe chain extender. In certain embodiments, the MFHC ratio may bealtered to adjust the hardness of the gel (i.e., an increase in the MFHCmay increase the hardness). In certain embodiments, the MFHC value isgreater than 0.2, 0.3, 0.4, or 0.5. In some embodiments, the MFHC valueis between 0.2 and 0.5. In other embodiments, the MFHC value is between0.3 and 0.4.

The overall amount of hydride components in the gel can also vary. Theratio of hydride to vinyl components (provided by the base polymer) canbe defined as “H/V.” In other words, H/V is the total moles of hydride(contributions from crosslinker and chain extender) divided by theamount in moles of vinyl from the base polymer (e.g., V-PDMS) present.In certain embodiments, the dry silicone gel has a H/V ratio between 0.5and 1.0, between 0.6 and 1.0, between 0.7 and 1.0, between 0.8 and 1.0,or between 0.9 and 1.0. If the H/V ratio is greater than 1, this meansthat there are more hydride groups present in the system than vinylgroups. In theory, the dry silicone gel will have a maximum hardnesswhere the H/V ratio is 1 (this is the theoretical point where all thegroups react with each other.) However, in practice this is not alwaysthe case and the maximum will be situated in the neighborhood of H/Vequals 1.

A theoretical representation depicting the relation between hardness ofthe dry silicone gel and the H/V ratio is shown in FIG. 5. In certainembodiments, the region of interest (or “ROI”) for the dry silicone gelcomprises slightly less hydrides than vinyl groups (i.e., the H/V isless than but close to 1). This is because gels with H/V values greaterthan 1 can undergo undesired post-hardening of the gel. With the help ofthe stoichiometric curve shown in FIG. 5, the relationship between theamount of hydride groups and the amount of vinyl can be calculated toget a certain hardness. This value can be used to obtain the differentamount of reagents needed to make a gel with the wanted hardness.

A schematic overview of the reaction is depicted in (V) below, whereinthe crosslinker compounds are represented by “+,” the chain extendercompounds are represented by “=,” and the base polymer V-PDMS compoundsare represented by “−.” In certain embodiments, the chain extender mustalways connect two different base polymer compounds, or connect to onebase polymer and terminate the chain on the opposite end.

Catalyst

In certain embodiments, an addition cure catalyst is used to assist inreacting the base polymer, crosslinker, and chain extender. Performingthe reaction without using a catalyst is typically a very energyconsuming process. Temperatures of 300° C. or even higher are needed inorder to avoid the produced gel to have poor and inconsistent mechanicalproperties.

In certain embodiments, the catalyst includes a Group VIII metal. Inother embodiments, the catalyst comprises platinum. Platinum catalystcan be prepared according to methods disclosed in the art, e.g., Lewis,Platinum Metals Rev., 1997, 41, (2), 66-75, and U.S. Pat. No. 6,030,919,herein incorporated by reference. In another embodiment, the catalyst isa homogenous catalyst. In other embodiments, the catalyst is aheterogeneous catalyst. Examples of heterogeneous catalysts includeplatinum coated onto carbon or alumina.

In one embodiment, the catalyst is “Karstedt's catalyst.” This is aplatinum catalyst made of Pt complexed withdivinyltetramethyldisiloxane, shown below in (VI).

An advantage of this catalyst is the fact that no heterogeneous reactionis taking place but that the catalyst will form a colloid. An advantageof these catalysts is the fact that only a small amount (ppm level) isneeded. This reduces the cost of the polymerization process.

In another embodiment, the catalyst may be a rhodium chloride complex,e.g., tris(triphenylphosphine)rhodium chloride (“Wilkinson's catalyst”).

Rhodium based catalysts may require higher concentrations and higherreaction temperatures to be successful to a large extent. But poisoningcomes together with reactivity; and therefore rhodium based catalystsmay be less easily poisoned than platinum catalysts.

In yet other embodiments, the catalyst may be a carbonyl derivation ofiron, cobalt, and nickel. In one embodiment, the catalyst isdicobaltoctacarbonyl CO₂(CO)₈. High temperatures (e.g., >60° C.) shouldbe avoided in order to prevent decomposition and deactivation of thecatalyst. In comparison to the Pt catalyst, here 10⁻³M are needed in thecase of Pt which is 10⁻⁶M or ppm level. Also the reactivity is sloweddown by a factor of 5.

The catalytic reaction mechanism is a Lewis-mechanism. First, there is acoordination of oxygen to the catalyst in the presence of thecrosslinker or chain extender. This step is called the induction period.This gives hydrogen and the platinum colloid. Next, the chain extenderor crosslinker will precede the attack of the vinyl group. By doingthis, an electrophile complex is formed. The vinyl group (V-PDMS) thenwill act as a nucleophile. Combining both the vinyl-group of the V-PDMSchain with the crosslinker or chain extender that was bound to thePt-catalyst gives the silicone product. The hydride is transferred tothe second carbon of the vinyl group. The Pt-colloid is than availablefor reacting a second time. Oxygen can be seen as a co-catalyst becauseoxygen is not consumed in this reaction and the O—O is not broken in thereaction sequence.

Catalysts should be isolated from compounds that can poison, orotherwise harm, the catalyst's performance. For example, amines, thiols,and phosphates can all poison a catalyst such as a platinum containingcatalyst. Amines, thiols, and phosphates may form very stable complexeswith a catalyst, thereby slowing the reaction or altogether stopping thereaction.

Inhibitor

In certain embodiments, inhibitors are added in the silicone gelformulation to slow down the curing process. Slowing down the curingprocess allows more time to work with the polymer mixture duringprocessing, dispensing, and molding.

The inhibitor can bind to the catalyst and form a stable complex. Bydoing this, the Pt catalyst is deactivated. When the complex isactivated by adding energy (raising the temperature) the inhibitor willlose its binding for the Pt-catalyst. After this, the Pt-catalyst is inits activated form again and the polymerization reaction can start. Theinhibitor may help manipulate the gel before it fully cures and extendthe pot life. In certain embodiments, the pot life may be approximately1 hour at room temperature and 6-8 hours at 3° C.

In certain embodiments, the inhibitor comprises two electron-rich groups(alcohol- and allylfunction) forming an acetylenic alcohol. These groupscan interact with the catalyst and shield it from other reactive groups.In one embodiment, the inhibitor of a Pt-catalyst is3,5-Dimethyl-1-hexyn-3-ol, shown below in (VII).

Additives

In certain embodiments, the dry silicone gel composition may compriseadditional common components. For example, the compositions may includeadditives such as flame retardants, coloring agents, adhesion promoters,stabilizers, fillers, dispersants, flow improvers, plasticizers, slipagents, toughening agents, and combinations thereof. In certainembodiments, the additional additives may include at least one materialselected from the group consisting of Dynasylan 40, PDM 1922, Songnox1024, Kingnox 76, DHT-4A, Kingsorb, pigment, and mixtures thereof. Insome embodiments, the additives comprise between 0.1 and 25 wt % of theoverall composition, between 0.1 and 5 wt % of the overall composition,between 0.1 and 2 wt % of the overall composition, or between 0.1 and 1wt % of the overall composition.

In some embodiments, the compositions disclosed and by methods disclosedherein comprise a flame retardant. In certain embodiments, the flameretardant is zinc oxide. In some embodiments, the flame retardantcomprises between 0.1 and 25 wt % of the overall composition, between0.1 and 5 wt % of the overall composition, between 0.1 and 2 wt % of theoverall composition, or between 0.1 and 1 wt % of the overallcomposition. In one embodiment, the flame retardant comprises 20 wt % ofthe overall gel composition.

In some embodiments, the compositions disclosed and made by methodsdisclosed herein contain at least one stabilizer. Stabilizers includeantioxidants, acid-scavengers, light and UV absorbers/stabilizers, heatstabilizers, metal deactivators, free radical scavengers, carbon black,and antifungal agents.

Making the Dry Silicone Gel

In one embodiment, the dry silicone gel is prepared by mixing a firstset of components together, mixing a second set of components together,and then mixing the two sets of components together. The first set ofcomponents comprises blending the base polymer (e.g., V-PDMS) with thecatalyst. The second set of components comprises blending thecrosslinker and chain extender. The second set of components may alsocomprise blending additional base polymer, and in some embodiments, aninhibitor. In some embodiments, the first and/or second set ofcomponents may also comprise blending at least one of the additivesdiscussed above. In certain embodiments, the amount of catalyst presentin the first set of components is between 0.01-1 wt %, between 0.05-0.1wt %, or approximately 0.083 wt %. In some embodiments, the remainder ofthe first set of components is the base polymer.

Regarding the second set of components, in certain embodiments, theamount of crosslinker is between 0.1-1 wt %, between 0.2-0.4 wt %, orapproximately 0.3 wt %. In certain embodiments, the amount of chainextender in the second set of components is between 0.5-5 wt %, between1-3 wt %, or between 1.5-2.5 wt %. In some embodiments, the amount ofinhibitor in the second set of components is between 0.01-0.1 wt %,between 0.1-0.5 wt %, or approximately 0.04 wt %. In other embodiments,the amount of base polymer in the second set of components is between95-99.9 wt %, between 96-99 wt %, or between 97-98.5 wt %.

In certain embodiments, the amount of combined crosslinker and chainextender in the overall dry silicone gel is between 0.1-5 wt %, between0.5-2 wt %, between 0.75-1.5 wt %, or approximately 1.25 wt %.

The dry silicone gel is then prepared by mixing the first set ofcomponents with the second set of components. In one embodiment, theweight ratio of the blend of the first set of components to the secondset of components is approximately 1:1. In another embodiment, theweight ratio of the blend is between approximately 47.5:52.5 and52.5:47.5. Adjusting the ratio slightly can cause large differences inthe overall hardness of the dry silicone gel. For example, in certainembodiments, when the ratio is 52.5:47.5 between the first and secondset of components (wherein the second set of components comprisesV-PDMS, crosslinker, chain extender, and inhibitor), the hardness may belower than the hardness of the same composition at the 1:1 blendingratio. Additionally, in certain embodiments, when the ratio is 47.5:52.5between the first and second set of components, the hardness may begreater than hardness of the same composition at the 1:1 blending ratio.In one example, the hardness may be approximately 72 g at the 52.5:47.5ratio, 140 g at the 1:1 ratio, and about 210 g at the 47.5:52.5 ratio.In other words, a 2.5% variation may affect the hardness of the gel byas much as 70 g. Therefore, the weighing procedure during thepreparation of the gel composition needs to be carried out with a highprecision.

Uses and Properties of the Dry Silicone Gel

The dry silicone gels described herein may be used in a number of enduses due to their improved properties, such as improved behavior inmechanical stresses (e.g., vibration and shock) or ability to sealuneven or complicated structures (due to the ability to flow and adaptto the area of the structure). In certain embodiments, the dry siliconegels may be used in an interconnect, cover, or closure system. Inparticular, the dry silicone gel may be used in a fiber optic closure,electrical sealant, or electrical closure. In some embodiments, the drysilicone gels are used as gel wraps, clamshells, or gel caps. In furtherembodiments, the dry silicone gels are used in the inside of aresidence. In other embodiments, the dry silicone gels are used outsideof a residence. Use of the dry silicone gel within a closure orinterconnect system may allow for a reduction in the number ofcomponents, frame size, or cost over other sealing mechanisms.

In certain embodiments, the dry silicone gel is used as a flameretardant sealant. In one embodiment, the dry silicone gel comprises aflame retardant additive (e.g., zinc oxide) in order to function as aflame retardant sealant.

In certain embodiments, the dry silicone gel is used in a closuresystem. In certain embodiments, the closure system comprises a housing,a cable, and a dry silicone gel. In some embodiments, the cable is aLSZH cable.

In some embodiment, the system further comprises a connector, and, insome instances, a receptacle or port, therein forming an interconnectsystem. The interconnect system may comprise a mini input/outputconnector, data connector, power connector, fiber optic connector, orcombination thereof. For example, the interconnect system may comprise aRJ-45 connector system. Non-limiting examples of interconnect systemsand components are displayed in FIGS. 6, 7, 8, 9a, 9b, 10a, and 10b.

The dry silicone gel may be used to create a seal formed bydisplacement. In other embodiments, the dry silicone gel may be used tocreate a seal having radial functionality, axial functionality, or acombination thereof. In yet other embodiments, the dry silicone gel maybe used to create a seal formed by displacement and having radial and/oraxial functionality.

FIGS. 6, 7, and 8 provide non-limiting examples of radial and axialfunctionality. FIG. 6 displays an example of a connection hub havingmultiple connection receptacles or ports for the cables 16 within thehousings 14 to be connected. FIG. 6 displays both radial connectionports 10 and axial connection ports 12. FIG. 7 displays a connector 26;housing 18, 28; and cable 16 assembly with radial sealing 22. FIG. 8displays a connector 26; housing 32, 34; and cable 16 assembly withaxial sealing 30, wherein the seal follows the surface of the axial port12. In certain embodiments, the housing may have a knob 20 that may bepushed inward to engage the latch 24 on the connector 26, allowing theconnector to be removed from the port.

In certain embodiments, the dry silicone gel may be used to create aseal in a housing assembly having multiple parts. For example, in oneembodiment the dry silicone gel may be used in a straight two-piecehousing assembly, as shown in FIGS. 9a and 9b. In another embodiment,the dry silicone gel may be used in an angled two-piece housingassembly, as shown in FIGS. 10a and 10b.

The dry silicone gel may be sealed around the cable 16 by sliding asmaller diameter gel formation over the cable to create a seal throughinterference. In other embodiments, the seal may be created by moldingthe dry silicone gel around the inside of the housing components andthen snapping the housing, gel, and cable into place.

In some embodiments, the dry silicone gel is used in a closure orinterconnect system that is “compatible” with a low smoke zero halogen(LSZH) cable. In certain embodiments, compatibility is measured bysubjecting the sample to one or more mechanical or environmental teststo test for certain functional requirements. In some embodiments,compatibility is measured by passing a pressure loss test, tightnesstest, and/or visual appearance test. In certain embodiments, the drysilicone gel in the closure or interconnect system is compatible where atraditional thermoplastic elastomer gel would fail (as shown anddescribed in the examples and figures).

Tightness may be tested under International Electrotechnical Commission(IEC) Test 61300-2-38, Method A and IEC 60068-2-17, Test Qc. In certainembodiments, tightness is tested by immersing the specimen in a waterbath and using an internal pressure of 20-40 kPa (0.2-0.4 atm) for 15minutes. It is important that tightness is measured directly afterinstalling the closure at a temperature of −15° C. or 45° C. It is alsoimportant that all the air bubbles present on the outside of the closureare removed. If a continuous stream of air bubbles is observed, thismeans the specimen is not properly sealed and it will be considered as afailure (i.e., not compatible).

Pressure loss may be tested under IEC 61300-2-38, Method B. In certainembodiments, the gel and cable are compatible if the difference inpressure before and after the test is less than 2 kPa (0.02 atm).

Visual appearance may be tested under IEC 61330-3-1 by examination ofthe product with the naked eye for defects that could adversely affectthe product performance.

The sample may be subjected to various mechanical and/or environmentalconditions prior to testing tightness, pressure loss, visual appearance,etc. In certain embodiments, compatibility is determined by subjectingthe sample to one or more of the following mechanical tests: axialtension test, flexure test, re-entry test, and torsion test, and/or oneor more environmental tests: resistance to aggressive media test,resistance to stress cracking test, salt fog test, temperature cyclingtest, and waterhead test.

In certain embodiments, the sample is subjected to an axial tension testaccording to IEC 61300-2-4. In this test, the sample may be pressuredinternally at 20 kPa (0.2 atm) or 40 kPa (0.4 atm) at room temperatureand sealed. The base assembly is clamped and a force is applied to eachof the extending cables individually. If the sample has an outerdiameter of less than or equal to 7 mm, then the amount of force percable applied is equal to (outer diameter/45 mm)*500 Newtons (“N”). Thisforce is applied for 15 minutes for each cable and built up to the IEC61300-2-4 test. If the sample has an outer diameter of greater than 7mm, then the amount of force per cable applied is equal to (outerdiameter/45 mm)*1000 N, with a maximum of 1000 N applied. This force isapplied for one hour. Internal pressure is then examined for pressureloss. In certain embodiments, the gel and cable are compatible if thepressure loss is less than 2 kPa (0.02 atm). In addition, in certainembodiments, the gel and cable are compatible if the displacement of thecable is less than 3 mm. In other embodiments, the specimens are furthersubjected to the tightness test, previously described.

In other embodiments, compatibility is measured by subjecting the sampleto a flexure test according to IEC 61300-2-37. In this test, the samplesare subjected to temperatures of −15° C. and 45° C. Samples arepressured internally at 20 kPa or 40 kPa (0.2 atm or 0.4 atm) andsealed. Cables are bent individually at an angle of 30° (or a maximumforce application of 500 N) each side of neutral in the same plane. Eachbending operation is held for 5 minutes. The cable is returned to itsoriginal position and then the procedure is repeated in the oppositedirection. After 5 cycles on each cable, the samples are visuallyinspected by the naked eye for appearance, conditioned at roomtemperature, and subjected to a tightness test. In some embodiments, thegel and LSZH cable are compatible if the specimen passes the visualappearance test, pressure loss test (i.e., less than 2 kPa (0.02 atm)),and/or tightness test.

In another embodiment, compatibility is measured by subjecting thesample to a re-entry test according to IEC 61300-2-33. In certainembodiments, re-entry can be simulated after a certain time oftemperature cycling. To complete this test, the closure has to beremoved from the cycling room and tested on tightness. After this areentry test can be done. In this test, a dummy plug or cable is removedfrom the closure and another cable or dummy plug is added. Then,tightness is measured again. Re-entry is successful if the closurepasses the tightness test again.

Another mechanical test may be employed to determine compatibility. Thesample may be subjected to a torsion test according to IEC 61300-2-5.After completion of the torsion test, the gel and cable may beconsidered compatible if the sample passes the visual inspection test,pressure loss test, and/or tightness test.

In yet other embodiments, compatibility is measured by conducting anenvironmental test of temperature cycling or accelerated aging under IEC61300-2-22 and IEC 60068-2-14, Test Nb. In one embodiment, thetemperature cycling test is conducted on the cable jacket between thegel blocks by cycling the temperature between −40° C. and 70° C. for 10days at two cycles between the extreme temperatures per day. In someembodiments, the humidity is uncontrolled, the dwell time is four hoursand the transition time is two hours. In certain embodiments, the cablejacket is tested for maintenance of tensile strength, ultimateelongation, tightness, visual appearance, and/or re-entry. Also, incertain embodiments, after the temperature cycling test, tightness ofthe closures needs to be tested after being conditioned to roomtemperature for a minimum of 2 hours. Therefore, in certain embodiments,the gel and LSZH cable are compatible if the specimen passes thetightness test.

In another embodiment, compatibility is determined by subjecting thesample to a resistance to aggressive media test under EEC 61300-2-34,ISO 1998/I, and EN 590. The sample is considered compatible if itsubsequently passes the tightness and/or appearance test.

In yet another embodiment, compatibility is determined by subjecting thesample to a resistance to stress cracking test under IEC 61300-2-34. Thesample is considered compatible if it subsequently passes the tightnesstest and/or shows no visible signs of cracking.

In other embodiments, compatibility is determined by subjecting thesample to a salt fog test under IEC 61300-2-36 and IEC 60068-2-11, TestKa. The sample is considered compatible if it subsequently passes thetightness and/or appearance test.

In some embodiments, compatibility is determined by subjecting thesample to a waterhead test under IEC 61300-2-23, Method 2. The sample isconsidered compatible if there is no water ingress.

In certain embodiments, the dry silicone gel has measurable properties.For example, in some embodiments, the dry silicone gel has a hardness inthe range of 26 to 53 Shore 000 Hardness, or 100 to 300 g, as measuredaccording to methods known in the art. In certain embodiments, the shorehardness gauge is measured according to ISO868 or ASTM D2240. In otherembodiments, hardness can be measured on a texture analyzer. Forexample, a LFRA Texture Analyzer-Brookfield may include a probe assemblyfixed to a motor driven, bi-directional load cell. In such a system, theprobe is driven vertically into the sample at a pre-set speed and to apre-set depth. The hardness is the amount of force needed to push theprobe into the test sample. In other embodiments, the dry silicone gelhas a hardness in the range of 37 to 45 Shore 000, or 160 to 220 g. Inyet other embodiments, the dry silicone gel has a hardness in the rangeof 38 to 42 Shore 000, or 170 to 200 g.

For further example, in some embodiments, the compression set, asmeasured after 50% strain is applied for 1000 hours at 70° C., has arange between 4% and 20%. In other embodiments, the compression set, asmeasured after 50% strain is applied for 1000 hours at 70° C., has arange between 10% and 14% when measured according to the modifiedversion of ASTM D395, method B described above.

In some embodiments, the gel is compressed with a certain strain ordeformation (e.g., in certain embodiments, to 50% of its original size).This causes a certain stress in the material. The stress is now reducedbecause the material relaxes. In certain embodiments, the stressrelaxation of the dry silicone gel has a possible range between 30 and60% when subjected to a tensile strain or deformation of about 50% ofthe gel's original size, wherein the stress relaxation is measured aftera one minute hold time at 50% strain. In other embodiments, the stressrelaxation of the dry silicone gel is between 40% and 60% when subjectedto a tensile strain of about 50%. A higher stress relaxation indicatesthat once a gel is installed in a closure, the gel will require lessstress in order for it to seal.

In certain embodiments, the dry silicone gel composition has less than10% oil bleed out over a period of time when the gel is undercompression of 120 kPa (1.2 atm) at 60° C. In certain embodiments, oilbleed out is measured on a wire mesh, wherein the oil loss may exit thegel through the mesh. The weight of the gel sample is recorded beforeand after the pressure has been applied. In some embodiments, the gelhas less than 8% oil bleed out over the period of time. In otherembodiments, the gel has less than 6% oil bleed out over the period oftime. In certain embodiments, the oil loss is measured at 200 hours, 400hours, 600 hours, 800 hours, 1000 hours, 1200 hours, or 1440 hours (60days).

In certain embodiments, the dry silicone gel has less oil bleed out incomparison to a thermoplastic gel over the same period of time at 120kPa (1.2 atm) at 60° C. In some embodiments, the dry silicone gel has40%, 50%, or 60% oil bleed out than the thermoplastic gel at 200 hours,400 hours, 600 hours, 800 hours, 1000 hours, 1200 hours, or 1500 hours(about 60 days).

EXAMPLES

Dry silicone gels were synthesized according to the following examples.A first set of components was prepared. To prepare the first set ofcomponents, a platinum catalyst complex (Karstedt catalyst, CAS-number68478-92-2) from Sigma-Aldrich N.V./S.A., Bornem, Belgium, is added to acontainer. Vinyl-terminated polydimethylsiloxane (CAS-number 68083-19-2)from ABCR GmbH & Co. KG, Karlsruhe, Germany, is combined with thecatalyst in a ratio of 100:0.0311.

The catalyst is added first, this compound needs to be added to thebottom of the container and make sure no catalyst is splashed onto thesides. After adding the catalyst the V-PDMS can be added by pouring itinto the container until about 10 grams from what needs to be weighedout. The last 10 or more grams are added with more precision by the useof a large pipette or syringe. It is best to start mixing at low rpm(100 rpm) and gradually increasing to 500 rpm in 2 minutes. After the 2minutes mixing, the mixing speed can be increased to 1200-1400 rpm for 3minutes.

To prepare a second set of components, a vinyl-terminatedpolydimethylsiloxane (CAS-number 68083-19-2) from ABCR GmbH & Co. KG isadded to a crosslinker, GELEST SIT 7278.0, a chain extender GELESTDMS-H03, and an inhibitor, ALDRICH 27, 839-4. The crosslinker is addedto the container first, because small variations in the added amount cangreatly influence the hardness of the gel. If too much is added, thiscan always be sucked out again. Next, the inhibitor is added to thereaction container. The third component that needs to be weighed out isthe chain extender. It is best to start mixing at low rpm (100 rpm). In2 minutes go to 500 rpm and scrape off the sides of the container with aplastic rod. After this 2 minutes of mixing, the mixing speed can beincreased to 1200-1400 rpm for 3 minutes.

The first set of components was mixed with the second set of componentsat 1:1 ratio in a vial. The two sets of components were mixed at 1250rpm for 2-3 minutes, placed under vacuum for 4-5 minutes, and pouredinto the desired mold. The resulting molded mixture was placed undervacuum for 3 minutes and then cured for 30 minutes at 90° C. Drysilicone gels were made according to the following Examples 1-6.

Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Wt. % Wt. %Wt. % Wt. % Wt. % Wt. % 1st Set of Components Gelest 99.917 99.91799.917 99.917 99.917 99.917 DMS-35, vinyl Catalyst 0.083 0.083 0.0830.083 0.083 0.083 2nd Set of Components Gelest 98.079 97.636 97.59397.509 97.467 97.439 DMS-35, vinyl Gelest SIT 0.329 0.279 0.284 0.2940.299 0.302 7278.0, crosslinker Gelest 1.552 2.045 2.083 2.157 2.1942.219 DMS-H03, chain extender Aldrich 0.040 0.040 0.040 0.040 0.0400.040 27,839-4, inhibitor Hardness 40 g 75 g 95 g 145 g 180 g 205 g

While not implemented in these Examples, in certain embodiments,additional additives may be added to the first set of components. Insome embodiments, the additional additives may include at least onematerial selected from the group consisting of Dynasylan 40, PDM 1922,Songnox 1024, Kingnox 76, DHT-4A, Kingsorb, pigment, and mixturesthereof. In some embodiments, the additives comprise between 0.1 and 5wt %, between 0.1 and 2 wt %, or between 0.1 and 1 wt % of the first setcomposition.

For further example, the first and second sets of components were mixedat 10 ratios from 47.5:52.5 to 52.5:47:5. Dry silicone gels were testedunder controlled conditions in a closure system used in underground andaerial applications to repair fiber cables up to 12 fibers.

Dry silicone gels were further tested under controlled conditions in aclosure system including a fiber organizer and cable closure used infiber optic cables in above and below-ground environments. In addition,dry silicone gels were tested under controlled conditions in a closureorganizer and multi-out system for cables having a small diameter.

The dry silicone gels were tested in a number of ways: temperaturecycling, re-entry test, French water cycling, cold and hotinstallations, and kerosene exposure. For temperature cyclingexperiments, closures including dry silicone gels were exposed totemperatures between −30° C. and +60° C. for 10 days. Humidity was notcontrolled. The closures were cycled between the high and lowtemperatures two times a day for ten days. Samples were maintained atthe extreme temperatures for four hours during each cycle.

For combined temperature cycling tests, dry silicone gels were installedin three closure systems. After installation the closures were tested ontightness and put into temperature cycling. After eight days a re-entrytest was performed and after ten days the closures were taken out ofcycling, tested on tightness and re-entry. Closures containing thestandard thermoplastic gels were also tested.

For tightness testing, the closure is immersed in a water bath for 15minutes and an internal pressure of 20 kPa. If air bubbles are observed,this means the closure is not properly sealed and it will be consideredas a failure.

For re-entry testing, a dummy plug or cable is removed from the closureand another cable or dummy plug is added. Then, tightness is measuredagain. Re-entry is successful if the closure passes the tightness testagain.

In certain embodiments, the dry silicone gel in the closure system isable to pass the tightness and re-entry tests where a traditionalthermoplastic elastomer gel would fail (as shown and described in theexamples and figures).

FIG. 1 shows the hardness (g) verses stress relaxation (%) of drysilicone gels as measured on a TA-XT2 texture analyzer from TextureTechnologies (Westchester County, N.Y.). The squares provide examples ofgels that are tight and re-enterable; the red triangles provide examplesof gels that fail on tightness and/or re-entry. The solid oval in thebottom left of the graph indicates examples of traditional thermoplasticelastomer gels. The solid oval to the right indicates a specific regionfor dry silicone gels. Three examples of dry silicone gel are shownwithin the oval. The dotted oval indicates an extended range ofacceptable dry silicone gels.

FIG. 2 shows the stress relaxation (%) versus the compression set (%) ofdry silicone gels over 1000 hours at 70° C. The compression set wasmeasured using a modified version of ASTM D395, method B. As opposed tousing samples with a diameter of 29 mm a thickness of 12.5 mm, sampleswere measured having a diameter of 28 mm and thickness of 12 mm. Thesquares provide examples of gels that are tight and re-enterable; thered triangles provide examples of gels that fail on tightness and/orre-entry. The solid oval on the left of the graph indicates examples oftraditional thermoplastic elastomer gels. The solid oval to the lowerright indicates a specific region for dry silicone gels. Three examplesof dry silicone gel are shown within the oval. The dotted oval indicatesan extended range of acceptable dry silicone gels.

FIG. 3 shows the hardness (g) versus the compression set (%) of drysilicone gels over 1000 hours at 70° C. Again, compression set wasmeasured with the modified version of ASTM D395, method B describedabove. The squares provide examples of gels that are tight andre-enterable; the red triangles provide examples of gels that fail ontightness and/or re-entry. The solid oval on the left of the graphindicates examples of traditional thermoplastic elastomer gels. Thesolid oval to the lower right indicates a specific region for drysilicone gels. Three examples of dry silicone gel are shown within theoval. The dotted oval indicates an extended range of acceptable drysilicone gels.

Oil loss'experiments were also conducted on dry silicone gels withhardness of 140 g, 170 g, and 200 g. FIG. 4 shows the oil bleed-out offive gels under compression at a pressure of about 120 kPa (about 1.2atm) and at a temperature of about 60° C. The gels labeled Si H 140, SiH 170, and Si H200 are dry silicone gels having hardnesses of 140 g, 170g, and 200 g, respectively. The gels labeled L2912 and L2908 areexamples of thermoplastic elastomer gels. The silicone gel with ahardness 200 g (Si H200) had the lowest amount of oil loss. After 1,500hours, about 60 days, the oil loss for these dry silicone gels isbetween 8 and 10%. For hardness 200 g the oil loss was slightly lessthan 6%. The oil loss for the L2912 thermoplastic gel is about 16% after1,500 hours. The data in FIG. 4 represents a reduction of 50% in oilloss compared to these thermoplastic gel systems.

Although examples have been described herein, it should be appreciatedthat any subsequent arrangement designed to achieve the same or similarpurpose may be substituted for the specific examples shown. Thisdisclosure is intended to cover any and all subsequent adaptations orvariations of various examples. Combinations of the above examples, andother examples not specifically described herein, may be apparent tothose of skill in the art upon reviewing the description.

The Abstract is provided with the understanding that it will not be usedto interpret or limit the scope or meaning of the claims. In addition,in the foregoing Detailed Description, various features may be groupedtogether or described in a single example for the purpose ofstreamlining the disclosure. This disclosure is not to be interpreted asreflecting an intention that the claimed examples require more featuresthan are expressly recited in each claim. Rather, as the followingclaims reflect, inventive subject matter may be directed to less thanall of the features of any of the disclosed examples. Thus, thefollowing claims are incorporated into the Detailed Description, witheach claim standing on its own as defining separately claimed subjectmatter.

The above disclosed subject matter is to be considered illustrative, andnot restrictive, and the appended claims are intended to cover all suchmodifications, enhancements, and other examples, which fall within thetrue spirit and scope of the description. Thus, to the maximum extentallowed by law, the scope is to be determined by the broadestpermissible interpretation of the following claims and theirequivalents, and shall not be restricted or limited by the foregoingdetailed description.

What is claimed is:
 1. A method of making a dry silicone gel comprising:providing a first set of components comprising: (1) a base polymerhaving a vinyl- silicone vinyl-silicone group, and (2) an addition curecatalyst; providing a second set of components comprising: (1) acrosslinker having three or four Si-H groups, (2) a chain extenderhaving two Si-H groups, and (3) additional base polymer having avinyl-silicone group; and mixing the first and second set of componentstogether to form the dry silicone gel, wherein the dry silicone gel hasa hardness between 100 g and 300 g, and a mole fraction of hydridepresent as crosslinker between 0.2 and 0.5, wherein the base polymer andadditional base polymer are each a vinyl-terminated polydimethylsiloxaneeach having a molecular weight between 28,000 g/mol and 70,000 g/mol. 2.The method of claim 1, wherein the second set of components furthercomprises an inhibitor.
 3. The method of claim 2, wherein the inhibitoris 3,5-dimethyl-1-hexyn-3-ol.
 4. The method of claim 1, wherein thefirst and/or second set of components further comprises at least oneadditive selected from the group consisting of: flame retardants,coloring agents, adhesion promoters, stabilizers, fillers, dispersants,flow improvers, plasticizers, slip agents, toughening agents, andcombinations thereof.
 5. The method of claim 1, wherein the dry siliconegel comprises between 0.1 wt % and 25 wt % of a flame retardantadditive.
 6. The method of claim 5, wherein the flame retardant additiveis zinc oxide.
 7. The method of claim 1, wherein the base polymer andadditional base polymer each have one or more of the followingproperties: (a) a viscosity between 500 mm²/s and 165,000 mm²/s; and (b)a vinyl content between 0.01 mmol/g and 0.1 mmol/g.
 8. The method ofclaim 1, wherein the dry silicone gel comprises one or more of thefollowing properties: (a) a stress relaxation between 40% and 60% whenthe gel is subjected to a deformation of 50% of its original size; (b) acompression set between 4% and 20% after 50% strain has applied to thegel for 1000 hours at 70° C.; and (c) less than 10% oil bleed out afterbeing under compression of 1.2 atm for 60 days at 60° C.
 9. The methodof claim 1, wherein the crosslinker is selected from the groupconsisting of tetrakis(dimethylsiloxy)silane,methyltris(dimethylsiloxy)silane, and combinations thereof.
 10. Themethod of claim 1, wherein the chain extender is selected from the groupconsisting of hydride containing polydimethylsiloxane, dihydridecontaining siloxane, hydride terminated polyphenylmethylsiloxane,hydride terminated polydiphenylsiloxane, functionalized terminatedsilicone, and combinations thereof.
 11. The method of claim 1, whereinthe hydride to vinyl ratio in the dry silicone gel is between 0.8 and1.0.
 12. The method of claim 1, wherein the catalyst is selected fromthe group consisting of platinum complexed withdivinyltetramethyldisiloxane, cobalt carbonyl complex, and rhodiumchloride complex.
 13. The method of claim 1, wherein the weight percentratio between the first set of components and the second set ofcomponents is 1:1.
 14. A method of making a dry silicone gel comprising:providing a first set of components comprising: (1) a vinyl-terminatedpolydimethylsiloxane having a molecular weight between 28,000 g/mol and70,000 g/mol, a viscosity between 3,000 mm²/s and 7,000 mm²/s, and avinyl content between 0.01 mmol/g and 0.1 mmol/g, and (2) an additioncure catalyst, wherein the catalyst is selected from the groupconsisting of platinum complexed with divinyltetramethyldisiloxane,cobalt carbonyl complex, and rhodium chloride complex; providing asecond set of components comprising: (1) a crosslinker selected from thegroup consisting of tetrakis(dimethylsiloxy)silane,methyltris(dimethylsiloxy)silane, and combinations thereof, (2) a chainextender selected from the group consisting of hydride containingpolydimethylsiloxane, dihydride containing siloxane, hydride terminatedpolyphenylmethylsiloxane, hydride terminated polydiphenylsiloxane,functionalized terminated silicone, and combinations thereof, (3) aninhibitor, and (4) additional vinyl-terminated polydimethylsiloxanehaving a vinyl-terminated polydimethylsiloxane having a molecular weightbetween 28,000 g/mol and 70,000 g/mol, a viscosity between 3,000 mm²/sand 7,000 mm²/s, and a vinyl content between 0.01 mmol/g and 0.1 mmol/g;and mixing the first and second set of components together to form thedry silicone gel, wherein the dry silicone gel has a mole fraction ofhydride present as crosslinker between 0.2 and 0.5, wherein the hydrideto vinyl ratio in the dry silicone gel is between 0.8 and 1.0, andwherein the weight percent ratio between the first set of components andthe second set of components is 1:1, and wherein the dry silicone gelhas a hardness between 100 g and 300 g.
 15. A dry silicone gel preparedfrom a composition comprising: a base polymer having a vinyl-siliconegroup, wherein the base polymer is a vinyl-terminatedpolydimethylsiloxane having a molecular weight between 28,000 g/mol and70,000 g/mol; a crosslinker having three or four Si-H groups; and achain extender having two Si-H groups, wherein the dry silicone gel hasa hardness between 100 g and 300 g, and a mole fraction of hydridepresent as crosslinker between 0.2 and 0.5.
 16. The dry silicone gel ofclaim 15 further comprising at least one additive selected from thegroup consisting of: flame retardants, coloring agents, adhesionpromoters, stabilizers, fillers, dispersants, flow improvers,plasticizers, slip agents, toughening agents, and combinations thereof.17. The dry silicone gel of claim 16, wherein the flame retardantadditive is zinc oxide.
 18. The dry silicone gel of claim 15, whereinthe crosslinker is selected from the group consisting oftetrakis(dimethylsiloxy)silane, methyltris(dimethylsiloxy)silane, andcombinations thereof.
 19. The dry silicone gel of claim 15, wherein thechain extender is selected from the group consisting of hydridecontaining polydimethylsiloxane, dihydride containing siloxane, hydrideterminated polydimethylsiloxane, hydride terminatedpolyphenylmethylsiloxane, hydride terminated polydiphenylsiloxane,functionalized terminated silicone, and combinations thereof.
 20. Thedry silicone gel of claim 15 having a hydride to vinyl ratio between 0.8and 1.0.
 21. The dry silicone gel of claim 15, wherein the dry siliconegel comprises between 0.1 wt % and 25 wt % of a flame retardantadditive.
 22. The dry silicone gel of claim 15, wherein the base polymerhas one or more of the following properties: (a) a viscosity between 500mm²/s and 165,000 mm²/s; and (b) a vinyl content between 0.01 mmol/g and0.1 mmol/g.
 23. The dry silicone gel of claim 15, wherein the gelcomprises one or more of the following properties: (a) a stressrelaxation between 40% and 60% when the gel is subjected to adeformation of 50% of its original size; (b) a compression set between4% and 20% after 50% strain has applied to the gel for 1000 hours at 70°C.; and (c) less than 10% oil bleed out after being under compression of1.2 atm for 60 days at 60° C.; and (d) the hardness is 160 to 220 g.